Lower SSD Write Bandwidth on c6525-25g Node

[Yacqub Mohamed]

Hi,

I've been running disk-heavy experiments with c6525-25g nodes, and the sequential write bandwidth with `dd` and my own C microbenchmarks is only 3 Gbps, whereas each SSD for the node is specified to be 6G. Even `dmesg` shows the SATA link as 6G. 

Is the node using SATA II, or am I configuring something incorrectly? Any help would be appreciated.

[Mike Hibler]

6Gbps is the theoretical speed of the bus. That particular disk (Micron
MTFDDAK480TDN) shows 460MB/sec as its sequential write speed. That is
around 3.7Gbps, which is about what you are seeing.

You will need to use a machine with NVMe drives if you want to get much
higher than what you are seeing. Or use multiple drives if it is aggregate
throughput you are interested in.

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